differentiating the first and last mental exercise step 1

Hi there!

I have just started IIH but have been meditating for quite some time. I was trying to figure out how two of the exercises in step 1 differ. From what i understand (from Bardon and wider reading), the first exercise is a simple mindfulness meditation - watching the thoughts as a casual unattached observer with curiosity. You just let the thoughts rise and fall - basically taking an inventory of all that is coming up.

How does this differ from thought control, the third exercise. From my understanding, Bardon isnt saying we need to have 0 thoughts; but must be able to silence the mind. In this case, if a thought pops up, would we be required to just notice it and take our attention away from it, letting it pass by (through focusing on the breath or just resting in awareness?) I feel like I intuitively do this when doing exercise 1 when i am consciously present (if i am sleepy, its another matter).

Have i got the understanding right?